First girlfriend lied to me about being raped so she could break up with me without guilt. Fucked my best friend a week later. She would call me up drunk at parties, whispering into the phone and telling me how she was going to fuck some guy, and when I would call her a bitch or whatever she would yell to her friends (once mutual friends) that I was being an asshole and hand the phone off to them, where they would call me a psycho and tell me to leave her alone, because apparently she thought it gave her an edge to have a "psycho-ex". She would talk shit about my dead brother, and laugh about my periods of abuse to try and get me mad to give credit, and I had just taken myself of medication for the time in my life before I met her, so it was overwhelming to say the least. I was only 18 or 19.
I had also just recently met my biological mother, with her help. She would message her, tell her how crazy I am, and did everything in her power to just make me look pathetic and weird.
It gets even better. A few years later I had an actual life ending scenario that I was dealing with, and I had just got the news a day prior. My "best-friend" (same one) drove down once he heard, but then got drunk and dragged me over to her place. I stupidly smoked weed for the first time in 5 years before we went in, so I was uncomfortable, and way too stoned. They just talked shit the whole time about me like I wasn't even there, and then locked themselves in the bathroom together in front of me. I left immediately, and had an even worse experience waiting for my ride. I eventually had to call an ex who I had just gotten out of a relationship with to pick me up an hour away.
She still drunk dials me, still adds an Y to the end of my name which makes me irrationally angry, and she still has no idea why I would possibly hate her as much as I do. I've tried being cool with her, because there's no sense in harboring a bunch of that, but she literally does not get it. There's soooo much other stuff that I don't really want to get into, but those are the highlights. She really set the trend for trust issues, and suspicions throughout the rest of my relationships.